18th August 2009 - Batavia, IL..Fermilab proton source and the Cockcroft-Walton preaccelerator...The process of particle acceleration begins with a small bottle of hydrogen located in the electrostatic Preaccelerator...Cockcroft and Walton observed that helium nuclei were emitted from lithium. A lithium nucleus penetrated by a hydrogen nucleus breaks up into two helium nuclei, which are emitted with high energy, in nearly opposite directions...Photo Credit: Heather A. Lindquist/SIPA....